Method and algorithm for predicting leak rates

Abstract

A method and algorithm for predicting the fluid loss rate of a system, uses data for the leak rate from the system for a substitute fluid that leaks at a different rate than the system fluid. In the illustrated embodiment, the system is a pneumatic tire and the substitute fluid is helium gas. The helium leak rate data is used in a Fortran program to predict the air loss rate from the tire by determining the leak rate factor f’ for helium, as compared to air, and using ‘f’ to calculate the air loss rate.

What is claimed is:  
     
       1. A method for calculating system fluid loss from a tire system based on measured fluid loss of a substitute fluid from the tire system, the tire system comprising a tire having structural parameters including a tire inner volume and a tire outer volume, the method comprising the steps of: 
       (a) obtaining data identifying a fluid loss rate of the substitute fluid from the tire system;  
       (b) using the data to calculate a rate factor f for the substitute fluid which defines the factor by which the leak rate of the substitute fluid is different from the leak rate of the system fluid;  
       (c) using the rate factor f with the gas law equation PV=nRT and the tire structural parameters to calculate the expected tire system fluid loss in the tire system.  
     
     
       2. The method of  claim 1  which includes the further step of comparing the calculated system fluid loss with a predetermined value. 
     
     
       3. The method of  claim 2  which includes the further step of providing a first signal if the calculated value is acceptable as compared to the predetermined value, and providing a second signal if the calculated value is not acceptable as compared to the predetermined value. 
     
     
       4. The method of  claim 1  wherein step (a) includes obtaining data for the substitute fluid, including the substitute fluid loss rate, change in concentration of the substitute fluid within the chamber with time, pressure, system inner volume, system outer volume, and chamber volume. 
     
     
       5. The method of  claim 1  which further includes obtaining data representing the substitute fluid leak rate as a function of variable liner parameters including liner butyl rubber (BR) content, distance of the liner ending from the toe, and liner gauge; using the data to calculate a rate factor f for the substitute fluid as a function of the variable liner parameters, and using the calculated rate factors f with the gas law equation to calculate the expected tire system fluid loss in the system as a function of the liner parameters. 
     
     
       6. The method of  claim 1  which comprises the further step of calculating a mean factor for f. 
     
     
       7. The method of  claim 1  which comprises the further step of calculating tire build to build differences in the system fluid loss rate due to variation in the tire structural parameters. 
     
     
       8. The method of  claim 1  which comprises the further steps of outputting measurements for the substitute fluid and the prediction for the system fluid. 
     
     
       9. A method for calculating system fluid loss from a tire system based on measured fluid loss of a substitute fluid from the tire system, the tire system comprising a tire having measurable structural parameters including a tire inner volume, a tire outer volume, and pressure, the method comprising the steps of: 
       (a) positioning the tire system containing the substitute fluid within a test chamber;  
       (b) obtaining data identifying a substitute fluid loss rate from the tire system into the chamber;  
       (c) using the data to calculate a rate factor f for the substitute fluid which defines the factor by which the leak rate of the substitute fluid is different from the leak rate of the system fluid;  
       (d) using the calculated rate factor f with the gas law equation PV=nRT to calculate the expected tire system fluid loss in the tire system.  
     
     
       10. The method of  claim 9 , wherein the tire system further including a liner having measurable liner parameters including liner material composition; a position of the liner end point; and liner gauge, the method further includes: 
       varying at least one of the liner parameters and obtaining data identifying a substitute fluid loss rate as a function of the varied liner parameter;  
       using the data to calculate a rate factor f for the substitute fluid as a function of the varied liner parameter; and  
       using the calculated rate factor f to calculate the expected system fluid loss in the tire system as a function of the varied liner parameter.  
     
     
       11. The method of  claim 9  which further includes: 
       varying at least one of the tire structural parameters and obtaining data identifying a substitute fluid loss rate as a function of the varied liner parameter;  
       using the data to calculate a rate factor f for the substitute fluid as a function of the varied tire structural parameter; and  
       using the calculated rate factor f to calculate the expected system fluid loss in the tire system as a function of the varied tire structural parameter.